Junqing Hu

Growth of SiC nanorods at low temperature

Cubic-phase SiC (β-SiC) nanorods were synthesized through a one-step reaction under pressure at 400 °C by which the crystalline product can be obtained directly without annealing at high temperature. The reaction was carried out in an autoclave by using SiCl4 and CCl4 as reactants and metal Na as coreductant. The x-ray diffraction pattern indicates the formation of β-SiC and x-ray photoelectron spectra display the stoichiometric relation between Si and C. Transmission electron microscopy images reveal that the product consists of nanorods with diameters from 10 to 40 nm and lengths up to several micrometers.

A hydrothermal reaction to synthesize CuFeS2 nanorods

Abstract A hydrothermal reaction route has been developed to prepare chalcopyrite phase CuFeS2 nanorods at 200–250°C. X-ray powder diffraction and transmission electron microscopy results reveal that the CuFeS2 synthesized displays nanorods with diameters of 20–40 nm and lengths of up to several micrometers. Elemental analysis gives the atomic ratio of Cu:Fe:S of 1:1.04:2.11. The 57Fe Mossbauer spectrum exhibits a six-peak hyperfine magnetic spectrum and a like-splitted line non-magnetic peak. The factors influencing the formation of the CuFeS2 nanorods were discussed.

Preparation and phase control of nanocrystalline silver indium sulfides via a hydrothermal route

A hydrothermal route was proposed to prepare and control nanocrystalline silver indium sulfides (orthorhombic AgInS 2 , tetragonal AgInS 2 , and cubic AgIn 5 S 8 ). The reaction was carried out in an autoclave in the temperature range of 100–280 °C with AgCl, InCl 3 , and thiourea as reactants. X-ray powder diffraction patterns and transmission electron microscopy images showed that the products were AgInS 2 and AgIn 5 S 8 phases and well crystallized with grain diameter in the range of 20–70 nm. X-ray photoelectron spectra of the single AgIn 5 S 8 phase revealed the surface stoichiometry (AgIn 5.05 S 8.11 ), and its room temperature Raman spectrum showed a strong peak at 130 cm −1 and a weak peak at around 290 cm −1 . The influence of reaction temperature on the phases in the final products was investigated. A possible reaction mechanism of the formation of silver indium sulfides was also briefly discussed.

Fabrication of BiTeI submicrometer hollow spheres

BiTeI submicrometer hollow spheres with diameters of 200–300 nm have been synthesized by an iodine transport hydrothermal method without the use of template materials or surfactants. The preparation was carried out in an autoclave in the temperature range 190–200 °C with Bi2Te3 and I2 as reactants. X-Ray powder diffraction patterns and transmission electron microscopy images show that the product is BiTeI with a hollow sphere structure. The sphere wall is composed of BiTeI nanoparticles with an average diameter of 5 nm and a thickness of ca. 10 nm. A possible growth mechanism for the hollow structure is proposed. The first excitonic peak of the BiTeI hollow spheres is considerably blue shifted in comparison with the band gap of the bulk material, which can be attributed to quantum confinement effects.

A convenient hydrothermal route to mineral Ag3CuS2 nanorods

Abstract A convenient hydrothermal route is proposed for synthesizing mineral Ag3CuS2 nanorods. X-ray powder diffraction (XRD) patterns indicated the formation of Ag3CuS2, and elemental analysis and X-ray photoelectron spectra (XPS) revealed the stoichiometric relation between Ag, Cu, and S. Transmission electron microscope (TEM) images demonstrated that the final product consisted of nanorods with diameters from 30 to 150 nm and lengths from 200 nm to 1 μm. A possible formation mechanism of Ag3CuS2 nanorods was proposed.

Gallium nitride synthesis from sodium azide using iodine as a heat sink and diluent

Nanocrystalline GaN has been synthesized from the solid-state reaction of GaI3 and NaN3 using I2 as heat sink and diluting the reactants. X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) revealed that the synthesized GaN crystallized in a hexagonal crystal structure and displayed spherical particles with an average size of 30 nm. X-ray photoelectron spectra (XPS) of the powder sample of as-prepared GaN gave the surface stoichiometry of GaN0.94. Room temperature photoluminescence (PL) spectrum showed that as-prepared GaN had one broad weak emission peak at 365 nm. The influence the addition of I2 had on the formation of GaN was investigated, and a possible reaction mechanism was also discussed.

The co-reduction route to TiC nanocrystallites at low temperature

Abstract TiC nanocrystallites have been synthesized through a co-reduction process by using TiCl 4 and CCl 4 as reactants and metal Na as co-reductant. The reaction was carried out in an autoclave at 450°C, which is much lower than those of traditional methods. X-ray diffraction pattern indicates that the obtained sample is cubic phase TiC. Transmission electron microscopy imaging reveals that it is produced as nanoparticles with a narrow size distribution (10–20 nm).

Nanodiamond formation by hot-filament chemical vapor deposition on carbon ions bombarded Si

Nanocrystalline diamond films were grown by a two-step process on Si(1 0 0) substrate, which was first pretreated by pure carbon ions bombardment. The bombarded Si substrate was then transformed into a hot-filament chemical vapor deposition (HFCVD) system for further growth. Using the usual CH4/H-3 feed gas ratio for micro crystalline diamond growth, nanodiamond crystallites were obtained. The diamond nucleation density is comparable to that obtained by biasing the substrate. The uniformly distributed lattice damage is proposed to be responsible for the formation of the nanodiamond

The synthesis of CuFeSe2 through a solventothermal process

Abstract A solventothermal process has been developed to prepare CuFeSe 2 nanocrystallites at 230°C with CuCl, FeCl 3 ·6H 2 O and Se powders as starting materials. The effect of solvent on the product has been studied and in our experiments, pyridine is the only solvent that can lead CuFeSe 2 to be obtained. The final product was characterized by X-ray diffraction (XRD), Mossbauer spectroscopy and transmission electron microscopy (TEM).

Solvothermal reaction route to nanocrystalline semiconductors AgMS2 (M=Ga, In)

Nanocrystalline semiconductors AgGaS2 and AgInS2 with particle sizes ranging from 5 to 12 nm are prepared by a solvothermal reaction in the temperature range 180–230 °C.